First measure out the rice crispies in a large bowl with half of the sprinkles, and grease a 9 x 13 pan so you’ll be ready when the marshmallow mixture is done.
Melt the butter and marshmallows just until melted on the stove top or in the microwave, but don’t over cook or they will get tough quickly.
Then stir in the dry cake mix a little at a time, but once again, try not to over stir so that the mixture will stay pliable.
Pour the marshmallow mixture over the rice crispy mixture and mix well. Then pat it into your 9×13 pan and sprinkle the remaining sprinkles over the top.